Cosmetic prosthetic hand



July 24s 31951 T. www@ HAL @95629333 COSMETIC PROSTHETIC HAND FiledOCT.. 2l, 1947 3 Sheets-Shet l Juy 24%? E951 E. T. LARKANS ET AL255515383 cosMETIc PROSTHETIC HAND Filed oct. 21, 1947 s sheets-sheet :s

Patented July 24, 1951 COSMETIC PROSTHETIC HAND Edward T. Larkins,Daytona Beach, Fla., Bernard S. Thomas, Washington, D. C., and David R.

Fetters, Hyattsville, Md.

Application October 21, 1947, Serial No. 781,111)

12 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370G. 757) The present invention relates generally to prosthetic devicesand more particularly to a self-I closing prosthetic hand mechanismwhich 'simulates the gripping action of the human hand,

and is adapted to be covered by a cosmetic plastic glove which closelysimulates the color, texture, conguration, and appearance of the "humanhand.

A difficulty encounted in prosthetic hands of this character heretoforedevised has been in combining high utility value with naturalappearance. A further difficulty has been in providing a mechanism whichis easy to operate and which has a grip of suicient strength for normaluse.

In the device of the present invention these difficulties have beensubstantially obviated in that the mechanism is constructed and arrangedto follow closely the skeletal formation and finger movement of thehuman hand, and, therefore, is particularly adapted for use with theaforementioned cosmetic plastic glove. The mechanism is also especiallyadapted for use with a shoulder-operated cable mechanism in that thehand mechanism is normally spring-urged toV the closed position, therebyobviating a tedious and continuous pull on the cable while holdingobjects with the hand. The finger structure of the mechanism ismechanically arranged to provide anti-friction devices at certain of thejoints thereof whereby the fingers are moved to an open position by asmall pull on the cable, a quality particularly desirable Where it isnecessary to grasp and release objects frequently.

An object of the present invention is tol provide a new and improvedprosthetic hand mechanism for use with a cosmetic plastic glove.

Another object is to provide a prosthetic hand mechanism which closelysimulates the skeletal formation and movement of the human hand.

Still another object is to provide a prosthetic hand mechanism which isoperated by a small pulling force.

A further object is to provide a prosthetic hand mechanism in which thefinger structure is normally spring-closed.

A still further object is to provide a springclosed prosthetic handmechanism in which the finger structure is operated throughout themovement thereof by a more nearly uniform pulling; force.

A still further object is to provide a prosthetic hand mechanism whichis light in weight, simple in design, and durable in operation.

vStill further objects, advantages, and improve- 2 ments will becomeapparent from the followin detailed description taken in connection withtheaccompanying drawings in which: Fig. 1 is a plan view of the deviceof the present invention according to a preferred em`I the mechanismtaken along line 2-2 Fig. 6 is a sectional View taken along line 6-6 ofFig. 5;

ig. 7 is a sectional view taken along line 1 1 of Fig. 4; and

Fig. 8 is a sectional view takenalong line 8'-8 of Fig. 5.

Referring now to the drawings in which like numerals of reference areemployed to indicate like parts throughout the several views,l there isprovided a mechanism generally indicated l5 and including a supportingdisk Il), Yperforated las at ll to decrease the weight thereof andhaving a threaded hollow attaching-shank l2 adapted to receive a nut I3.The shank l2 and nut I3 serve to secure the disk lil to a conventionalarm boot Ill which may be fastened to thearm stump of' the wearer in anywell known manner.

The `mechanism I5 also includes a frame mem-` ber I6 attached to thedisk IG by means of a screw Il. A locking pin I8 extends through disk land into frame member I6, thereby to prevent rotation of the framemember withx respect to the;

disk.

The frame member I6 is for'medwith areduced portion I9 to receive a campulley 2|.l A pivot pin 22 is press-fitted into a boref23 I'of portionI9. Pin 22 receives anti-friction bearing 24 of cam pulley 2| which isheld against displacement by a screw 25 positioned in one end ofthe pin22. Cam pulley 2i has secured theretov` an eccentrically mounted pin 26,the purpose which will be hereinafter more fully des'zribec'i.-y Thebody member I6 is formedl at c me e z 11lwith an angular extension 2lhavingacutportion 28 adapted to receive'-a--bearingjcap secured theretoby screws 3| and 32: Exten Sion 21 has a' birfurcated end adaptedft'v'otatably receive a transversely disposed `rodl3 3.-'

Fixedly mounted on rodv 33 andia 'similar-'rod' "34 are four archedfinger bars 35, 35, 31, -'and which- 3 are Shaped to follow the skeletalformation of the human lingers. This construction insures unitary actionof the four finger bars about the axis of rod 33. Finger bar 36 has anopening 39 formed therein to accommodate a pin 4l. A bifurcated' linl:I42. is pivoted o n pin 4l and has one end of a connecting bar 43pivotally attached thereto as at 44. lihe other end of connecting( bar43 is pivotally joined to cam pulley 2| by theA aforementioned pin 26.

Fastened as at 40 to the pulley 2l is a cable 45 which passes around aportion ofthe peripheryl of the pulley, through an opening 5l)v inthedisk i0' and continues up the arm of the wearer to the usual shoulderoperating mechanism (not shown). It will be apparent that when cable 45is pulled, pulley 2l is rotated, thereby causing movement of the fingerbars to an open or non-gripping, position as the pull on the cable is.transmittedv through pin 26, connecting bar 43, and link 42.

It, further will be@ apparent that any desired opening of thefinger barsmay be made. by governing the amountof pull. on the cable 45.

'Ihecampulley is so shaped as to provide. an eiective torque arm which.increases, Fig. 4, as the, pulley isJ rotated and the, tension. of thenger actuating springs is increasedwhereby the nger.. structure isadapted to be operated throughout the movement thereof by a morenear-12S(y uniform pull. on the cable.

It, beseen inFig. 4. of the drawings that when the nger structure in theclosed position, the pivotal axes. ofthe. pulley, bar, and linkv arein.substantial alignment; thereby providing a substantially7 irreversiblelock, that is, the nger structure can. be moved by a pull on cable 45and cannot readily be moved by a pull on the fingers themselves, thusthere is little likelihood of the linger structure inadvertentlyreleasing smal-1 articles heldv thereby.

In order to bring the finger bars to the closed ov. gripping positionandalso to provide a strong gripforthe 'finger bars there are provided apair of springs. 46 mounted4 0n a, Shaft 4l which is. rotatably mountedin complementary halves of a.. bore.- 48.v in; angular extension 21. andbearing cap: 2li. The. shaft llll has formed therein a pair of:transverse slots 49,Y adapted to receive one end of. each ofthe springs46 respectively. The.

springs, are secured toshaft. 41 by transverse pins 66. An importantfeature of the device is the reduction of.A friction by providinganti-friction..

thumb bar. over and above thatwhich would. be f applied thereto i-f. thesprings. were mounted on shaft 33 with the, same tension in the closedposition.y for the:l reason that, by interposing pivotal shaft. 33between shafts. 34 and, 41, the lever arm of each of springs. 4.6decreases as the finger structure is opened, whereby the force appliedto. the finger structure byv the, springs further. increases asY thelinger structure is. progressively opened; The foregoing arrangement hasthe advantage that the gripping force, between. the thumb bar andtheringer structure increases asy larger and heavier objects are graspedtherebetween.`

Mounted; at one end of the shaft. 4.1 isa toothed ratchetwheel 5.2which, is engaged by a. paw-l lli 4 53 mounted on shaft 54 rotatablyheld in complementary halves of the bore 55 in extension 21 and cap 29.The end of shaft 41 is formed as at 56 to receive a key (not shown) forthe purpose of adjusting the tension on springs 46.

Secured to the, body member I6v and;v at one side thereof by screws5-1fand 58 isa thumb bar 594 Which is bent to follow generally theskeletal formation of the human thumb the tip thereof comingtoa pointsubstantially midway of the tips of finger bars 35 and 36 and extendingslightly therebeyond. As Will be seen in Fig. 8, theV screw 5,3*v may beused to adjust the thumb bar 59 to the position desired. A purpose ofthe above arrangementl is to provide a convenient means of preadjustingthe position of thumb bar 53 so as to facilitate the gripping of smallobjects such as pencils, pens, etc. The thumb bar may. be rigidlyattached to the frame, in which case angular adjustment of the bar maybe effected` by heating. and. bending.

Aeuard platenV is. secured t0 the angular.: ex tension 21. by screw 3l.to: prevent the ratchet mechanism.. and.- Sprihgs: from becomingentangled... in aA glove-or cover 6i.- to be hereinafter` more, fullydescribed..

In order. to provide aprosthetic. handhaving a,

natural appearance the cover or glove 6i isused; with the device of thepresen-t invention. rEhe glove, lV is composed, of ailexibleplastic.mate-fV rial` wlfiicl'i` closely simulates; the. color;- textura and.appearance of the human skin. It is.I formed. by a molding process,l themolds being produced by` aprocess in which, a; human. hand is used'toprovide the form and detail thereof.. A glove is, therefore provided.which, has substantially au. the intricate details, of. the. human handas well,V as.A the ,estheticl character thereof.

The glove 6 I. has a pal- 1n portion 62 which covers;

, the major part of the mechanism t5, a, thumb.

portion 63. which covers the thumbl b ar 5 3, and; finger portions 6,4,65,.4 66, and 61 which cover theI finger bars 3,5L 36, 31 and 38.respectively'. Wrist portion 6.8, is formed witha slit 6 9.- to. fa;-cilitate the application or removal of the glove. slide fastenerv 'Hfis. Provided. t0. close the. slit,-

The glove 6 l.. is formed ofaiiexible semi-elastic plastic material,A inorder to. provide; a Covering.; for the mechanism which. appeals totheesthetic. senses, and, also, accommodates the movement; of the..mechanism Without undue distortioni of the glove. Inv order to. preventexcessivev wear of the glove 6.|- in service and to QQOperate with theglove in providing an improved griplng medium,A resilient llers 15formed ofa suitabler material such, for example, as. foam plastic aremounted on the. finger.- bars and; the thumb bar and are disposedrespectively within the. lingers.

l and thumb of the. glove.

It. also a. feature ci theihvehtioh that the cam pulley 2i has formed;on the ne-,liphery thereof a radial shoulder 'i3 for contact with thelslrroullder-y 'llion framel i6 in order tol proyide a Stan to preventexcessive opening. 0fV the mecha,-

nism. It is, of course, understood.- thatwhile the. device of thepresent invention has. beenk shown beibe-y arraneed for attachment, tothe right arm, the mechanism and: glove may be made-in f reverseorderfor usel with, the left arm.

From the foregoing, it should now be appre- @lated that a. prosthet,hand. mechanism has been provided. whichV the thumb and. fingerstructure may be formed of a light and strong material. such. forexample, as. magnesium whereby v,these partsv may be vprovided with4sufficient strength to retain their initial hand simulatingcharacteristics notwithstanding a Wide diversity A of use and to avoidpermanent strains and distortion resulting from accidental bending ofthe parts in service, while at the same time providing a skeletal handstructure of light Weight and precise mechanical movement.

Whereas a preferred embodiment of the invention has been disclosed inparticularity herein which gives satisfactory results, it will beapparent that additional embodiments and modifications thereof mayVoccur to those skilled in the art without departing from the spirit andscope as defined by the appended claims.

The invention herein described and claimed may be manufactured and usedby or for the Government of the United States of America forgovernmental purposes without payment of any royalties thereon ortherefor.

What isl claimed as new and desired to be secured by Letters Patent ofthe United States is: l l. A mechanism for a prosthetic hand, comprisingthe combination of a frame member, a thumb bar attached to said framemember, a finger structure mounted for pivotal movement on said framemember, yieldable means for urgin'g said finger structure toward saidthumb bar, said yieldable means increasing in tension as the fingerstructure is moved away from the thumb bar, link members attachedtogether and to said finger structure, a cam pulley mounted for rotationon said frame, and a cable passed around the pulley and secured theretofor coaction therewith, said pulley having an eccentric pin foroperative connection with the terminal one of said link members andbeing cam shaped in such a manner as to increase the leverage of thecable thereon as the tension of said yieldable means increases duringthe movement ofthe linger structure away from the thumb bar thereby toprovide a more nearly uniform tension on the cable throughout saidmovement of the finger structure.

2. A prosthetic hand mechanism, comprising i the combination of a frame,a thumb bar flxedly attached tosaid frame, a linger structure mountedfor pivotal movement on said frame, spring means for yieldably urgingsaid finger structure v toward said thumb bar, said spring meansincreasing in tension as the finger structure is moved away from thethumb bar, a cable operated cam-shaped pulley rotatably supported onsaid frame and link means interconnecting the pulley and the fingerstructure for moving the finger structure away from the thumb bar as thepulley is rotated by a pull on the cable whereby the leverage of thecable thereon is increased during movement ofthe finger structure awayfrom said thumb bar and a simulation of themovement of the human fingersis provided by a more'nearly uniform tension in the cable.

tensimV respectively for maintaining said shaft@` in la set positionthereby to vary the initial tension on said pair of springs, and means.including a. cable operated pulley having a peripheral cam surfacethereon in engagement with the cable for moving the finger structureaway from the thumb bar and concurrently therewith increasing theleverage of the cable with respect to the pulley in response to tensionapplied to thel cable. l

, 4. A prosthetic hand mechanism adapted to be covered by a cosmeticplastic glove, comprising, in combination, a frame member having anangular extension, a thumb bar attached to said frame member anddisposed within the thumb of the glove, a unitary finger structurepivotally mounted on said angular extension and adapted to be moved froma closed position to an open position with relation to said thumb bar,the

lingers of said nger structure being disposed,

within. the fingers of the glove, spring means for normally maintainingthe finger structure in the closed position, said spring meansincreasing in tension as the finger structure is moved to said openposition, means supported on said frame member and including a cableoperatedcamshaped pulley and a link connection between the pulley andthe linger structure for moving the finger structure to the openposition as the pulley is rotated by a pull on the cable, said pulleyhaving a cam-shaped periphery for increasing the effective leverage ofthe cable thereon as the tension in said spring means increases therebyto provide a more nearly uniform pull on the cable and simulation ofmovement of the human hand.

5. In a prosthetic hand mechanism adapted to be covered by a cosmeticplastic glove, the combination of a frame member having an angularextension thereon, a thumb bar attached to` said frame member, a lingerstructure mounted for pivotal movement on said angular extension andadapted to be moved with relation to said thumb bar, spring means fornormally maintaining said 'linger structure adjacent the thumb bar,ratchet means operatively connected to said spring means for varying thetension of said spring means, a cable, and means including apulley forcoaction with said cable and a link connection between the pulley andthe finger structure for providing an irreversible lock for the lingerstructure when in adjacency with the thumb bar and for movingthe fingerstructure away from the thumb bar against the opposing force of saidspring means` when aI sufficient pulling force is exerted onthe Cable. 5

6. A mechanism for a cosmetic prosthetic,l

ture away from the thumb bar, means including a cam-shaped pulleyrotatably supported on the frame, a cable secured to the pulley andpassed over a peripheral portion thereof for coactionV therewith and alink connection between the pulley and the'iinger structure for movingthe finger structure with relation to the thumb bar and in opposition tothe tension ofl said springs when the cable is pulled, said peripheralpor- ,tion ofthe pulley being cam shaped to increase aten-fees theei-ective leverage yof the 'cable on 'the :pulley as the tension in`said springs ,increases in :ree sponse to said movement of the .ngerstructure, and means including a ratchet and pawl mechanism operativelyconnected to said plurality of springs and adjustable at will forIvarying the tension of the springs in accordance with the degree lof:gripping force desired between the finger structure and the thumb bar.

'7. A .prosthetic Ihand mechanism Vfor use with a glove :simulating lthecolor, texture, fand contour of .the Ihuman hand, .comprising thecombination of aiframe member, a thumb barmounted on said frame member'and disposed within the thumb of the glove, :a ringer Ymechanism mountedfor pivotal .movement `on said frame 'member and having fingersrespectively disposed within the fingers 'of the glove, means .includingan adjust-- ing screw for moving 'the thumb bar laterally withv relation.to a pair of said .lingers of the finger mechanism, spring Ameansforyieldably and normally maintaining said -linger mechanism adjacent saidthumb bar, said spring 'means in' creasing in tension during movement ofthe :fin` ger mechanism away from the thumb bar., and means including afcable .and a cam-shaped coacting .pulley having said Icable wrappedthereon for .moving the vfing-er mechanism away .from the thumb bar,said pulley being cam shaped to provide an increasing lever action ofthe cable on the 'pulley as the ltension of the spring means increasesthereby to operate the linger mechanism throughout said movement thereofin response to a more nearly uniform tension applied to the cable.

8. In a cosmetic prosthetic hand, the combination with a vresilientplastic glove 'of a mechanized :skeletal thumb and nger structuredisposed therewi'thinand comprising a frame membei' having an angularextension, ringer bars simulating the skeletal formation of humanfingers, a'pair of transverse parallel rods for rigidly securing saidiinger bars 'in spaced relation simu lating the .fingers oi Ta partiallyclosed human hand, one of said pair of rods being journalled in saidangular extension transversely thereof thereby 'to .pivotally supportthe nger bars as a unit thereon, .a thumb bar simulating the humanIthumb and adjustably secured to said frame member for lateral bendingmovement with respect 'to said finger bars, the other of said pair ofrods having a plurality o'f anti-friction rollers carried thereon, ayshaft journalled in fthe Vang-ulai1 extension transversely thereof andparallel to said pair of rods, a plurality of coil springs secured .to`said shaft and having .arms extending into engagement respectively withsaid plurality of rollers so as to yieldably urge the finger bars intogripping relation with respect to said thumb bar and to .progressivelyincrease the tension in the 'springs as the finger bars areprogressively moved to open position with respect tothe thumb bar, aratchet wheel carried by the shaft -and a cooperating` pawl carriedbythe rangular exe tension for adjusting the tension in said 'springsupon rotation of the shaft, Va cable, a cam-shaped pulley .rotatablysupported on the angular eX- sion and secured to said `cable and having`the cable `wrapped thereon for coaction therewith, said pulley beingcam shaped in la manner to increase the leverage .of the cable on 'thepulley as the pulley is rotated upon pulling the cable, a crank pinsecured to the pulley, za rst link pivotally secured to one of saidStinger bars, and a second link pivotally interconnecting v'said cran-knin and Asaid first link, .said pulley andfsaid fijst andrsecond linksbeing constructed and arranged' to lresist opening yof the linger' :bars'from the closed position thereof by a for-ce applied thereto 9. Aprosthetic hand mechanism compri-sing, a support, -coact'ing thumb andfinger `structures respectively secured to and pivotally mounted Aonsaid support, a shaft journalled in the support parallel to the pivotallairis oi' the nger struc ture., :a plurality of anti-friction rollerscarried by the finger structure, said pivotal axis' ybeing disposedintermediatesaid shaft and said rollers, a 'plurality of coil springscarried by the-shaft-and having arms respectively extending intoengagementwith said .rollers so as to yieldably urge the lingerstructure into `gripping relation with vre spect to the thumb bar and toprogressively increase the tension 4in the springs as the fingerstructure is 4opened progressively with respect Lto the thumb bar, acable, a cam-shaped pulleyrotatably mounted on said support and` securedto the cable and having the cable Wrapped thereon for cooperationtherewith, said `pulley being ca-m shaped rin a manner to increase theleverage Iof the lcable on the pulley upon rotation thereof as the`cable, is pulled, and a linkage interconnecting the pulley and theiinger structure for pivotally' moving `the finger structure as thepulley is rotated.

l0. In a cosmetic prosthetic hand, the combi# nation of a resilientplastic glove and a mechanized skeletal thumb and linger structuredisposed therewithn and comprising a frame having an angular extension,nger bars simulating the skeletal formation of human vlingers mountedfor pivotal movement on said angular extension and respectivelyldisposed within the fingers of the" i the finger bars away lfrom thethumb bar, andmeans including a cable and a coacting /c'ainf shapedpulley secured to said cable and havin'g' the cable wrapped thereon formoving the finger bars away from the thumb bar in response to 'a pull'on the cable, said pulley being cam shaped to increase the leverage ofthe cable on the pulley thereby to compensate -iorsaid increase in ten-`sion of the spring means during said movement of the ringer bars. j

11. A mechanism for a prosthetic hand comprising, in combination, aframe member adapted to "be secured to the stump of a human arin, saidmovement with respect to `said thumb bar, a'bar extending through saidplurality of lingers adjacent said pivotal 'mounting and having apairjofanti-'friction rollers thereon, a shaft rotatably mounted in andextending beyond 'the sides said vframe member in spaced adjacency tosaid pivotal mounting, a pair-of'helical springs fixedly mounted 4onsaid s'haft respectively adjacent "the sides of said frame member andhaving extended ends thereof engaging said rollers, a ratchet 'wheelsecured to said shaft, a pawl mounted on said frame 'and engagingl theratchet lwheel whereby the initial tension `on'said springs isadjustably maintained, said springs yieldably urging said lingerstructure toward a gripping position with respect to the thumb bar andincreasing in tension as the nger structure moves to open position, aperipherally grooved -cam-shaped pulley, anti-friction means forpivotally mounting the pulley on said frame, a pin eccentrically mountedon the pulley, a link interconnecting said pin and said linger structureat a point slightly beyond said bar and for moving the ngers to saidopen position as the pulley is rotated, means including a cable forrotating said pulley, said cable having one end fastened to the pulleyand normally riding in said peripheral groove, said camshaped pulleybeing shaped to increase the lever arm thereof as the tension of saidsprings increases during movement of the lingers to said open positionthereby to provide a more nearly uniform pulling force on the cableduring movement of the finger structure to said open position.

12. A prosthetic hand mechanism comprising, in combination, a frame, athumb bar attached to the frame, a unitary finger structure pivotallysupported on said frame for pivotal movement 25 toward and away fromsaid thumb bar,r spring cured to the pulley and passed around aperipheral portion thereof, and link means interconnecting said ngerstructure and said cam pulley for moving the finger structure away fromthe thumb bar as the pulley is `rotated by a pull on the cable, saidperipheral portion being shaped to increase the leverage of the cable onthe pulley to compensate for said increase in tension of said springmeans as the pulley is rotated by the cable whereby the pull on thecable is rendered more nearly uniform during said movement of the lingerstructure away from the thumb bar.

EDWARD T. LARKINS. BERNARD S. THOMAS. DAVID R. FETTERS.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,225,415 Cronemiller May 8,191'7 1,507,680 Pecorella Sept. 9, 1924 2,409,884 Mollenhour Oct. 22,1946 FOREIGN PATENTS Number Country Date 163,514 Great Britain May 26,1921 319,058 Germany Feb. 23, 1920

